Generalized host/pathogen models have shown that pathogens can theoretically regulate host population dynamics, as well as have evolutionary impacts. At the same time, there has been little or no work done to measure ecological or evolutionary relationships between hosts and pathogens outside of human epidemiology or agricultural crop systems. The major goals of this proposal are 1) to develop population dynamic models relevant to plant host/pathogen systems, 2) to extend the theory to examine the effects of genetics on population dynamics, 3) to develop models that explore evolutionary impacts of pathogens on host life histories, 4) to experimentally determine the effects of density dependence in Silene populations, and 5) to establish long term experimental populations that allow model assumptions to be tested, thus acting as a guide to future theory development.